Circuit board

ABSTRACT

The invention provides a circuit board comprising a substrate and a dielectric material provided on the substrate. The dielectric material comprises (i) 40˜80 parts by weight of polyphenylene ether resin having a Mw of 1000˜7000, a Mn of 1000˜4000 and Mw/Mn=1.0˜1.8; (ii) 5˜30 parts by weight of bismaleimide resins; and (iii) 5˜30 parts by weight of polymer additives, wherein the dielectric material has Dk of 3.75˜4.0 and Df of 0.0025˜0.0045. The dielectric material is suitably used in prepregs and insulation layers of a circuit board, because it has high Tg, low thermal expansion coefficient, low moisture absorption and excellent dielectric properties such as Dk and Df.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending application Ser. No.13/845,908, filed on Mar. 18, 2013, for which priority is claimed under35 U.S.C. §120, the entire contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to a circuit board, particularly to a circuitboard having a resin composition.

2. Related Art

As developed with wireless transmission products and technologies oftransmitting high frequency, epoxy resin and novolak resin cannotsatisfied for the advance application, especially high frequency printedcircuit board (PCB). Fluorine-containing resin can be used as PCB withlow dielectric loss. However, fluorine-containing resin is expensive andnot easy to work, and thus limited to the use of military andastrodynamics. In addition, polyphenylene ether (PPE) resin hasexcellent mechanical property and dielectric property such as Dk and Df.Therefore, the PPE resins are preferable to be used a material for highfrequency PCB.

However, because the PPE resin is a thermal plastic resin, as applied ina copper-clad laminate, it may has disadvantages as follows: it is noteasy to work due to a high melting viscosity of PPE resin, interlayerfilm is easy released in a solvent clean step during a process formanufacturing PCB due to a poor solvent resistance of PPE resin, and itis not easy to operate above a temperature of 250° C. in solderingprocess due to melting point close to Tg. Therefore, PPE resin has to bemodified by curing so as to meet the requirement of using in PCB.

Curing modification of PPE resin generally has two manners: PPE resinmay become curable resin by introducing crosslinking active functionalgroups to molecular structure of PPE resin. Alternatively, PPE resin maybecome co-mixing curable composite material by introducing other curableresins to molecular structure of PPE resin with co-mixing modificationor interpenetrating network technology. However, PPE resin is likelyincompatible with the active functional groups or curable resins,because the polar difference exists in their chemical structures.Alternatively, PPE resin may lose the excellent properties, after itconducts curing modification with the active functional groups orcurable resins.

Therefore, there is a need to develop a circuit board having a materialthat has excellent dielectric properties and other properties such ashigh Tg, low coefficient of thermal expansion and low water absorptionof PCB requirement. Also, the material can be applied in the manufactureof high frequency PCB.

SUMMARY OF THE INVENTION

An object of the invention is to provide a circuit board having adielectric material with low dielectric loss, which has excellentdielectric properties, low coefficient of thermal expansion and lowwater absorption.

To accomplish the above object, there is provided a circuit board havinga dielectric material with low dielectric loss, which comprises (i)40˜80 parts by weight of polyphenylene ether resin having a Mw of1000˜7000, a Mn of 1000˜4000 and Mw/Mn=1.0˜1.8; (ii) 5˜30 parts byweight of bismaleimide; and (iii) 5˜30 parts by weight of polymeradditives, wherein the dielectric material has Dk of 3.75˜4.0 and Df of0.0025˜0.0045.

In the dielectric material with low dielectric loss of the invention,the polyphenylene ether resin is represented by the formula

wherein Y represents at least one C, O and benzene ring or thecombination.

In the dielectric material with low dielectric loss of the invention,bismaleimide resins are selected from groups consisting of

Phenylmethane maleimide

wherein n≧1;

Bisphenol A diphenyl ether bismaleimide

3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylethane bismaleimide

and

1,6-bismaleimide-(2,2,4-trimethyl)hexane.

In the dielectric material with low dielectric loss of the invention,the polymer additives are selected from groups consisting of

Homopolymers of Butadiene

wherein y=70% and x+z=30% ;

Random copolymers of butadiene and styrene

wherein y=30%, x+z=70% and w=≧1, and the amount of styrene=25 wt % ;

Maleimized Polybutadiene

wherein y=²⁸% and x+z=72%, the amount of maleic anhydride=8 wt %;

Butadiene-styrene-divinylbenzene copolymer, and

Styrene Maleic Anhydride copolymer

wherein X=1˜8 and n≧1.

In the dielectric material with low dielectric loss of the invention, itis preferable that crosslinking agent is added to increase crosslinkingdensity of resins. The crosslinking agents with 40-80 parts by weightmay be selected from the following groups consisting of

Triallyl isocyanurate (TAIC)

Triallyl cyanurate (TAC)

and

4-tert-butylstyrene (TBS)

In the dielectric material with low dielectric loss of the invention, itis preferable that catalyst is added to increase reaction ofcrosslinking agents and other resins. The catalysts includes at leastone peroxide having 116° C.-128° C. for a half life of 10 hours with 2-8phr based on the total weight of PPE, BMI, polymer additives andcrosslinking agents. The suitable peroxides comprise dicumyl peroxide,α,α′-bis(tert-butylperoxy)diisopropyl benzene and2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne.

In the dielectric material with low dielectric loss, it is preferablethat filler is added to increase thermal conductivity and mechanicalstrength, and reduce thermal expansion. The suitable fillers may befused silica, sphere-shaped silica, talc and aluminum silicate.

In order to increase flame retardation of the dielectric material of theinvention, halogen-containing flame retardants and flame retardantswithout halogen may be used. The halogen-containing flame retardants maycomprise decabromodiphenyl ethane. The flame retardants without halogenmay comprise phosphor-containing flame retardants and phosphates. Thephosphor-containing flame retardants and phosphates are produced byALBEMARLE CO., LTD. The phosphates are like tetrakis(2,6-dimethylphenyl)1,3-phenylene bisphosphate. tetrakis(2,6-dimethylphenyl) 1,3-phenylenebisphosphate can be represented by the formula,

[OC₆H₃(CH₃)₂]₂P(O)OC₆H₄OP(O)[OC₆H₃(CH₃)₂]₂.

The foregoing and other objects, features and advantages of the presentinvention will be apparent to those skilled in the art from thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

No drawings

DETAILED DESCRIPTION OF THE INVENTION

In one aspect of the present invention, there is provided a circuitboard having a thermal curable dielectric material to produce a prepregin a successive process in the following examples 4-1 to 4-7. Theprocess uses the dielectric material as a coating on a substrate whichmay be a fiberglass cloth. The apparatus for producing the prepregincludes a pasting tank wherein there are provided a plurality of rolls.The pasting tank is filled with the dielectric material. A roll offiberglass cloth may enter the pasting tank and pass the plurality ofrolls. The fiberglass cloth is sufficiently impregnated with thedielectric material, and then surplus dielectric material is removed bya metering roller. A heat treatment for curing the dielectric materialand removing the solvent is required at 100° C. to 350° C. for 1 minuteto 5 hours, preferably at 150° C. to 300° C. for 1 minute to 3 hours.The prepreg is obtained after the cured dielectric material is cooleddown and the fiberglass cloth is wrapped.

A double-sided copper-clad laminate is produced by providing severalprepregs in a neat stack between two electrodeposited copper foils,conducting a hot pressing process under 40 to 900 psi, raisingtemperature from 80° C. to 200° C. in 30 minutes, and then hot pressingat 200° C. for 120 minutes, and then cooling down to room temperature in30 minutes in a vacuum pressing machine. The prepreg includes afiberglass cloth of electrical grade 2116 and the dielectric material.Generally, a double-sided copper-clad laminate with a thickness of 1.0mm is produced by providing 4 sheets of prepregs in a neat stack betweentwo electrodeposited copper foils, with a thickness of 1.5 mm isproduced by providing 7 sheets of prepregs, and with a thickness of 2.0mm is produced by providing 10 sheets of prepregs.

The dielectric material of the present invention may form a stablehomogeneous solution in a solvent with a low boiling point. Theproperties of a copper-clad laminate with the dielectric material of theinvention were determined including Tg, heat decomposition temperature,heat decomposition time, solder heat resistance (288° C.), thermalexpansion coefficient, water absorption, thermal conductivity,dielectric constant, dielectric loss tangent and flammability accordingto IPC-TM-650 test method manual. The determining results show thecopper-clad laminate with the dielectric material of the invention hashigh Tg, excellent dielectric properties such as Dk and Df, low waterabsorption, high thermal resistance and high thermal conductivity. Thecopper-clad laminate is suitable used as a substrate for electronicelements and IC package.

EXAMPLES

TABLE 1 influence of PPE resin amount amount of PPE resin Example 4-1 C1C2 C3 C4 C5 C6 C7 PPE resin SA9000 60 52.5 45 41 37.5 34 22.5 BMI resin5100 15 15 15 15 15 15 15 Polybutadiene Ricon100 10 10 10 10 10 10 10Crosslinking TAIC 15 22.5 30 34 37.5 41 52.5 agents Flame XP7866, phr 2020 20 20 20 20 20 retardants fillers Fused silica, 20 20 20 20 20 20 20phr catalysts PEROXIDE 2.5 2.5 2.5 2.5 2.5 2.5 2.5 119° C. FOR A HALFLIFE OF 10 HRS Tg, TMA IPC-TM-650 206 224 229 221 212 213 212 2.4.24.3coefficient of IPC-TM-650 58/334 60/305 56/251 53/247 56/211 61/20455/245 thermal 2.4.24 expansion (α1/α2), ppm/ ° C. water PCT/121° C./0.29 0.33 0.34 0.34 0.39 0.39 0.40 absorption 1 hr 288° C. thermalDip288° C. >600 >600 >600 >600 >600 >600 >600 resistance Dk(2-10 GHz)Cavity 3.93 3.89 3.89 3.89 3.90 3.86 3.87 Df(2-10 GHz) Cavity 0.00570.0054 0.0048 0.0044 0.0040 0.0040 0.0039 flammability UL94 V-0 V-0 V-0V-0 V-0 V-0 V-0

Tg, Dk and Df were compared with different ratio and amount of PPE. TheTg level may be affected by the amount of PPE used. Also, the amount ofPPE may also have an affect on the Dk and Df value. When the amount ofPPE is high, Dk and Df may be high. When the amount of PPE is low, Dkand Df may be low. Typically, a low value for the Dk and Df ispreferred. In addition, the thermal expansion coefficient may be raisedwhen PPE is added, and BMI is added to balance the effect. In Table 1,part number SA9000 of PPE with chemical name of Polyphenylene Oxide(PPO) or Polyphenylene ether (PPE) is produced by Sabic CO., LTD.

TABLE 2 influence of BMI resin species and amount BMI resin ComparativeExample 4-2 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 examplePPE SA9000 42.5 40 37.5 35 32.5 37.5 37.5 37.5 37 37 37 37 37 37.5 37 50resin BMI 2300 0 0 0 0 0 0 15 0 8 0 8 0 0 5 4 0 resin 4000 0 0 0 0 0 150 0 8 8 0 8 0 5 4 0 5100 5 10 15 20 25 0 0 0 0 8 0 0 8 5 4 0 TMH 0 0 0 00 0 0 15 0 0 8 8 8 0 4 0 Poly- Ricon100 10 10 10 10 10 10 10 10 10 10 1010 10 10 10 0 butadiene Cross- TAIC 42.5 40 37.5 35 32.5 37.5 37.5 37.537 37 37 37 37 37.5 37 50 linking agents Flame XP7866, 20 20 20 20 20 2020 20 20 20 20 20 20 20 20 20 retardants phr fillers Fused 20 20 20 2020 20 20 20 20 20 20 20 20 20 20 20 silica, phr catalysts PEROXIDE 2.52.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 119° C. FORA HALF LIFE OF 10 HRS Tg, IPC-TM- 210 212 212 211 211 212 222 195 208204 205 200 214 210 207 218 TMA 650 2.4.24.3 coefficient IPC-TM- 60/ 58/56/ 54/ 50/ 55/ 45/ 45/ 50/ 57/ 45/ 52/ 54/ 53/ 49/ 64/325 of 650 296250 211 207 197 260 170 288 210 278 230 268 290 240 225 thermal 2.4.24expansion (α1/α2), ppm/° C. water PCT/ 0.33 0.34 0.39 0.44 0.46 0.410.47 0.33 0.43 0.42 0.41 0.36 0.44 0.40 0.39 0.33 absorption 121° C./1hr 288° C. Dip288°C. >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600thermal resistance Dk(2-10 Cavity 3.85 3.87 3.90 3.94 3.98 3.91 3.933.86 3.96 3.91 3.90 3.87 3.89 3.91 3.90 3.80 GHz) Df(2-10 Cavity 0.00400.0041 0.0040 0.0042 0.0043 0.0042 0.0046 0.0041 0.0041 0.0041 0.00450.004 0.0039 0.0041 0.0043 0.0044 GHz) flam- UL94 V-0 V-0 V-0 V-0 V-0V-1 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 mability

The coefficient of thermal expansion was measured with different speciesand amount of BMI resin. The more the amount of BMI resin is, the lowerthe coefficient of thermal expansion is. In the example, there are threekinds of comparison comprising three groups that A1-A5 shows differentamount of BMI with the same species, A6-A8 shows the same amount of BMIwith different species and A9-A 15 shows about the same total amount ofBMI with more than two species. In Table 2, part numbers 2300, 4000,5100 and TMH of BMI are produced by Daiwakasei Industry CO., LTD, inwhich part number 2300 has chemical name of phenylmethane maleimide,part number 4000 has chemical name of2,2′-bis[4-(4-maleimidophenoxy)phenyl]propane, part number 5100 haschemical name of 3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethanebismaleimide and part number TMH has chemical name of1,6′-bismaleimide-(2,2,4-trimethyl)hexane.

It can be found from group A1-A5 that by increasing the amount of BMIresin, the thermal expansion coefficient would decrease. However, byincreasing the amount of BMI resin, the water absorption would alsoincrease. As to group A6-A8, different BMI resins may reduce the thermalexpansion coefficient, but would also affect the water absorption.Regarding group A9-A15, different combination of BMI resins may reducethe thermal expansion coefficient, and affect the water absorption also.In the invention, the object of addition of BMI to the dielectricmaterial is to reduce the thermal expansion coefficient. However, themore the amount of BMI resin is, the higher the water absorption is.Therefore, the polymer additives are added to reduce the waterabsorption.

TABLE 3 influence of polymer additives species and amount polymeradditives Comparative Example 4-3 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12B13 example PPE resin SA9000 40 37.5 35 32.5 30 37.5 37.5 37.5 37.5 37.537.5 37.5 37.5 42.5 BMI resin 5100 15 15 15 15 15 15 15 15 15 15 15 1515 15 Polybutadiene Ricon100 5 10 15 20 25 0 0 0 0 0 0 0 0 0 Ricon130 00 0 0 0 10 0 0 0 0 0 0 0 0 MA8 Ricon150 0 0 0 0 0 0 10 0 0 0 0 0 0 0Ricon257 0 0 0 0 0 0 0 10 0 0 0 0 0 0 SMA S:M = 3:1 0 0 0 0 0 0 0 0 10 00 0 0 0 S:M = 4:1 0 0 0 0 0 0 0 0 0 10 0 0 0 0 S:M = 5:1 0 0 0 0 0 0 0 00 0 10 0 0 0 S:M = 6:1 0 0 0 0 0 0 0 0 0 0 0 10 0 0 S:M = 8:1 0 0 0 0 00 0 0 0 0 0 0 10 0 Crosslinking TAIC 40 37.5 35 32.5 30 37.5 37.5 37.537.5 37.5 37.5 37.5 37.5 42.5 agents Flame XP7866, 20 20 20 20 20 20 2020 20 20 20 20 20 20 retardants phr fillers Fused 20 20 20 20 20 20 2020 20 20 20 20 20 20 silica, phr catalysts PEROXIDE 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 119° C. FOR A HALF LIFE OF 10 HRSTg, TMA IPC-TM-650 221 212 200 194 186 213 217 211 220 215 210 206 195222 2.4.24.3 coefficient IPC-TM-650 53/201 56/211 64/220 67/260 74/30058/265 57/270 53/200 45/232 48/237 50/245 51/240 53/260 45/200 of 2.4.24thermal expansion (α1/α2), ppm/° C. water PCT/121° C./ 0.43 0.39 0.350.32 0.28 0.45 0.43 0.43 0.46 0.45 0.43 0.43 0.40 0.56 absorption 1 hr288° C. Dip288°C. >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600 >600thermal resistance Dk(2-10 GHz) Cavity 3.93 3.90 3.87 3.86 3.84 3.923.90 3.87 3.95 3.95 3.93 3.91 3.90 3.93 Df(2-10 GHz) Cavity 0.00430.0040 0.0041 0.0040 0.0039 0.0045 0.0044 0.0040 0.0085 0.0073 0.00640.0056 0.0042 0.0043 flammability UL94 V-0 V-0 V-0 V-1 V-1 V-0 V-0 V-0V-0 V-0 V-0 V-0 V-0 V-0

The water absorption was measured with different species and amount ofpolymer additives. Polybutadiene (PB) and styrene-maleic anhydride (SMA)were used as the polymer additives in the invention. It can be foundfrom using the different amount of PB with the same species that byincreasing the amount of PB, the water absorption would decrease.However, with the increasing amount of PB, the coefficient of thermalexpansion would also increase. As to using different species of PB incombination with SMA, it shows SMA can reduce the water absorption andthe coefficient of thermal expansion, but Df may remain high. However,PB can be used to reduce Df. In Table 3, part numbers Ricon100,Ricon130MA8, Ricon150 and Ricon257 of PB are produced by Sartomer CO.,LTD, in which part number Ricon100 has chemical name of butadienestyrene copolymer, part number Ricon130MA8 has chemical name ofbutadiene adducted with maleic anhydride, part number Ricon 150 haschemical name of polybutadiene resin and Ricon 257 has chemical name ofpolybutadiene grafted with styrene and benzene in toluene solution. InTable 3, SMA with S:M=3:1 indicates that the ratio of styrene to maleicanhydride is 3 to 1. Generally, the ratios are about 1:1˜12:1.

TABLE 4 influence of different species of crosslinking agents Example4-4 crosslinking agent D1 D2 D3 PPE resin SA9000 37.5 37.5 37.5 BMIresin 5100 15 15 15 polybutadiene Ricon100 10 10 10 Crosslinking TAC37.5 0 0 agents TAIC 0 37.5 0 TBS 0 0 37.5 Flame XP7866, phr 20 20 20retardants fillers Fused silica, 20 20 20 phr catalysts PEROXIDE 2.5 2.52.5 119° C. FOR A HALF LIFE OF 10 HRS Tg, TMA IPC-TM-650 183 212 2022.4.24.3 coefficient of IPC-TM-650 59/273 56/211 50/250 thermalexpansion 2.4.24 (α1/α2), ppm/° C. water absorption PCT/121 0.39 0.390.12 ° C./1 hr 288° C. thermal Dip288° C. >600 >600 >600 resistanceDk(2-10 GHz) Cavity 3.95 3.90 3.75 Df(2-10 GHz) Cavity 0.0039 0.00400.0035 Flammability UL94 V-0 V-0 V-0

The dielectric material of the invention may comprise at least onecrosslinking agent with 40-80 parts by weight selected from thefollowing groups consisting of Triallyl cyanurate (TAC), Triallylisocyanurate (TAIC) and 4-tert-butylstyrene. The properties of acopper-clad laminate with the dielectric material of the invention weremeasured with different species of crosslinking agents. It can be foundby using TAC that Tg and the coefficient of thermal expansion were poor,and water absorption, Dk and Df were of ordinary level. As to TAIC, allthe properties of a copper-clad laminate with the dielectric material ofthe invention were of ordinary level. Regarding 4-tert-butylstyrene, thecoefficient of thermal expansion, water absorption and Df wereexcellent, but Dk is low.

TABLE 5 influence of different species of flame retardants Example 4-5Flame retardants E1 E2 E3 E4 PPE resin SA9000 37.5 37.5 37.5 37.5 BMIresin 5100 15 15 15 15 polybutadiene Ricon100 10 10 10 10 Crosslinkingagents TAIC 37.5 37.5 37.5 37.5 Flame retardants DecabromodiphenylEthane, phr 10 0 0 0 XP7866, phr 0 20 15 10 Tetrakis(2,6-dimethylphenyl)0 0 5 10 1,3-phenylene bisphosphate, phr fillers Fused silica, phr 20 2020 20 catalysts PEROXIDE 119° C. FOR A 2.5 2.5 2.5 2.5 HALF LIFE OF 10HRS Tg, TMA IPC-TM-650 2.4.24.3 224 212 226 180 coefficient of thermalIPC-TM-650 2.4.24 55/233 56/211 65/267 67/339 expansion (α1/α2), ppm/°C. water absorption PCT/121° C./1 hr 0.43 0.39 0.37 0.30 288° C. thermalDip288° C. >60 >600 >600 >600 resistance Dk(2-10 GHz) Cavity 3.83 3.903.87 3.85 Df(2-10 GHz) Cavity 0.0043 0.0040 0.0040 0.0037 flammabilityUL94 V-0 V-0 V-0 V-0

If desired, the dielectric material of the invention may optionallycomprise flame retardants. A halogen-containing flame retardant ofdecabromodiphenyl ethane with 7-15 phr based on the total weight of PPE,BMI, polymer additives and crosslinking agents may be added to thedielectric material of the invention. The dielectric material of theinvention may comprise at least one flame retardant without halogen with12-14 phr based on the total weight of PPE, BMI, polymer additives andcrosslinking agents selected from the following groups consisting ofphosphor-containing flame retardants and phosphates. Thephosphor-containing flame retardants and phosphates are produced byALBEMARLE CO., LTD. The phosphates are like tetrakis(2,6-dimethylphenyl)1,3-phenylene bisphosphate.

TABLE 6 influence of different species of fillers Fillers Examples 4-6F1 F2 F3 F4 F5 F6 F7 PPE resin SA9000 37.5 37.5 37.5 37.5 37.5 37.5 37.5BMI resin 5100 15 15 15 15 15 15 15 polybutadiene Ricon100 10 10 10 1010 10 10 Crosslinking TAIC 37.5 37.5 37.5 37.5 37.5 37.5 37.5 agentsFlame XP7866, phr 20 20 20 20 20 20 20 retardants fillers Fused silica,phr 0 20 10 10 30 25 45 Ball type silica 20 0 10 0 0 0 0 catalystsPEROXIDE 119° C. 2.5 2.5 2.5 2.5 2.5 2.5 2.5 FOR A HALF LIFE OF 10 HRSTg, TMA IPC-TM-650 210 212 214 220 208 215 195 2.4.24.3 coefficient ofIPC-TM-650 53/220 56/211 52/225 58/260 45/210 50/220 40/205 thermal2.4.24 expansion (α1/α2), ppm/ ° C. water PCT/121° C./1 hr 0.41 0.390.40 0.39 0.38 0.40 0.36 absorption 288° C. thermal Dip288°C. >600 >600 >600 >600 >600 >600 >600 resistance Dk(2-10 GHz) Cavity3.87 3.90 3.88 3.85 3.96 4.01 4.06 Df(2-10 GHz) Cavity 0.0039 0.00400.0040 0.0040 0.0041 0.0043 0.0045 flammability UL94 V-0 V-0 V-0 V-0 V-0V-0 V-0

The dielectric material of the invention may optionally comprisefillers. The suitable fillers such as fused silica and sphere-shapedsilica may be used. The suitable amount of filler is 8-50 phr based onthe total weight of PPE, BMI, polymer additives and crosslinking agents.It can be found from the fused silica and the sphere-shaped silica withthe same amount that the sphere-shaped silica has lower Dk and Df thanthe fused silica.

TABLE 7 influence of different amount and species of catalysts catalystsExample 4-7 G1 G2 G3 G4 G5 G6 G7 G8 G9 PPE resin SA9000 37.5 37.5 37.537.5 37.5 37.5 37.5 37.5 37.5 BMI resin 5100 15 15 15 15 15 15 15 15 15polybutadiene Ricon100 10 10 10 10 10 10 10 10 10 Crosslinking TAIC 37.537.5 37.5 37.5 37.5 37.5 37.5 37.5 37.5 agents Flame XP7866, 20 20 20 2020 13 13 13 13 retardants phr fillers Ball type 20 20 20 20 20 13 13 1313 silica catalysts PEROXIDE 0 0 0 0 2.5 0 1.5 1.5 1 116° C. FOR A HALFLIFE OF 10 HRS PEROXIDE 2.5 3 7 8 0 0 0 1.5 1 119° C. FOR A HALF LIFE OF10 HRS PEROXIDE 0 0 0 0 0 2.5 1.5 0 1 128° C. FOR A HALF LIFE OF 10 HRSTg, TMA IPC-TM-650 212 220 222 227 208 225 220 209 215 2.4.24.3coefficient IPC-TM-650 56/21 53/22 49/22 50/18 57/23 50/23 47/22 52/2250/23 of thermal 2.4.24 1 5 0 0 0 0 6 0 5 expansion (α1/α2), ppm/° C.water PCT/ 0.39 0.43 0.47 0.60 0.42 0.38 0.40 0.42 0.38 absorption 121°C./1 hr 288° C. Dip288° C. >600 >600 >600 >600 >600 >600 >600 >600 >600thermal resistance Dk(2-10 GHz) Cavity 3.90 3.91 3.90 3.96 3.88 3.913.92 3.93 3.91 Df(2-10 GHz) Cavity 0.0040 0.0042 0.0045 0.0049 0.00390.0040 0.0041 0.0042 0.0039 flammability UL94 V-0 V-0 V-0 V-0 V-0 V-0V-0 V-0 V-0

The dielectric material of the invention may optionally comprisecatalysts including peroxides having 116° C.-128° C. for a half life of10 hours. The suitable amount of peroxide is 2-8 phr based on the totalweight of PPE, BMI, polymer additives and crosslinking agents. Thepreferable catalyst is a peroxide having 119° C. for a half life of 10hours.

The dielectric material of the invention may comprise PPE, but notcomprise epoxy resin. The desired values of Dk and/or Df cannot beobtained, if epoxy resin is added to the dielectric material of theinvention. When reacting epoxy resin with the dielectric material of theinvention, the open rings of the epoxy resin may produce excess OHgroups, therefore causing the Dk and Df value to remain high and unableto decrease.

What is claimed is:
 1. A circuit board comprising: a substrate; and adielectric layer provided on the substrate, wherein the dielectric layercomprises a dielectric material comprising polyphenylene ether (PPE)resin, bismaleimide resins and polymer additives.
 2. The circuit boardof claim 1, wherein the dielectric material comprises: (i) 40˜80 partsby weight of polyphenylene ether resin having a Mw of 1000˜7000, a Mn of1000˜4000 and Mw/Mn=1.0˜1.8; (ii) 5˜30 parts by weight of bismaleimideresins; and (iii) 5˜30 parts by weight of polymer additives, wherein thedielectric material has Dk of 3.75˜4.0 and Df of 0.0025˜0.0045.
 3. Thecircuit board of claim 2, wherein polyphenylene ether resin isrepresented by the formula

wherein Y represents at least one C, O and benzene ring or thecombination.
 4. The circuit board of claim 2, wherein bismaleimideresins are selected from groups consisting of Phenylmethane maleimide

wherein n≧1; Bisphenol A diphenyl ether bismaleimide

3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylethane bismaleimide

and 1,6-bismaleimide-(2,2,4-trimethyl)hexane


5. The circuit board of claim 2, wherein the polymer additives areselected from groups consisting of Homopolymers of Butadiene

wherein y=70% and x+z=30% ; Random copolymers of butadiene and styrene

wherein y=30%, x+z=70% and w=≧1, and the amount of styrene=25 wt % ;Maleimized Polybutadiene

wherein y=28% and x+z=72%, the amount of maleic anhydride=8 wt %;Butadiene-styrene-divinylbenzene copolymer; and Styrene Maleic Anhydridecopolymer

wherein X=1˜8 and n≧1.
 6. The circuit board of claim 2, wherein thedielectric material further comprises at least one crosslinking agentwith 40-80 parts by weight selected from the following groups consistingof Trially isocyanurate (TAIC)

Triallyl cyanurate (TAC)

and 4-tert-butylstyrene (TBS)


7. The circuit board of claim 2, wherein the dielectric material furthercomprises catalysts including at least one peroxide having 116° C.-128°C. for a half life of 10 hours with 2-8 phr based on the total weight ofPPE, BMI, polymer additives and crosslinking agents.
 8. The circuitboard of claim 7, wherein the catalysts including at least one peroxideselected from groups consisting of dicumyl peroxide,α,α′-bis(tert-butylperoxy)diisopropyl benzene and2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne.
 9. The circuit board ofclaim 2, wherein the dielectric material further comprises fillers with8-50 phr based on the total weight of PPE, BMI, polymer additives andcrosslinking agents selected from groups consisting of fused silica,sphere-shaped silica, talc and aluminum silicate.
 10. The circuit boardof claim 2, wherein the dielectric material further comprisesdecabromodiphenyl ethane with 7-15 phr based on the total weight of PPE,BMI, polymer additives and crosslinking agents.
 11. The circuit board ofclaim 2, wherein the dielectric material further comprises at least oneflame retardant without halogen with 12-14 phr based on the total weightof PPE, BMI, polymer additives and crosslinking agents selected from thefollowing groups consisting of phosphor-containing flame retardants andphosphates.
 12. The circuit board of claim 2, wherein the wherein thedielectric material has no epoxy.